Absorbent cellulosic products



Patented July 6, 1954 ABSORBENT CELLULOSIC PRODUCTS Walter Florus Reynolds, Jr., Stamford, Conn, as-

signor to American Cyanamid Company, New York, N. Y., a corporation of Maine N Drawing. Application February 10, 1948, Serial No. 7,531

\w I V \l The present invention relates to the manufacture of fibrous cell'ulosic articles and relates more 7 particularly to a method of improving the absorbency of felted fibrous cellulosic articles such as paper, and the like articles, by the addition thereto of a surface active agent prepared by reacting ethylene oxide and octadecylamine.

A primary object of the invention resides in the provision of a method of imparting improved absorbency and softness of hand to paper toweling and other cellulosic tissue products.

A further object of the invention is the provision of paper products containing certain surface active agents which, because of their substantivity for cellulose, may be incorporated in fibrous cellulosic materials during the wet formation of felted articles thereof, thus providing a more economical means of producing such articles than has heretofore been available to the art.

Another object of the invention is the provision of a method of overcoming, to a considerable extent, the sizing action caused in felted cellulosic products by the addition thereto of melamine-formaldehyde or other wet strengthproducing resins, and thereby producing felted cellulosic articles having improved absorbency with little or no loss in wet strength. Further 6 Claims.

though analyses of the exact retention have not been made, because of the small amounts of surface active agent employed, it is apparent from the greatly improved absorbency of the treated products that substantially all of the added agent is present in the products.

I have found that the best results are obtained by employing the products of reaction of .from about 2.5 mols to about 75 mols of ethylene oxide per mol of octadecylamine. These preferred surface active agents are produced by reacting an octadecylamine with the desired amount of ethylene oxide at a temperature within the range of from about 30 C. to about 100 C. at atmospheric pressure. If desired, the reaction may be carried out at relatively lower temperatures under from about 10 to about p. s. i. gage pressure. The octadecylamine employed may be an, entirely saturated pure compound or it may be a commercially produced compound containing considerable amounts of unsaturated octadecylamine.

objects will be apparent from the following de- 7 tailed description of the invention. I have discovered that felted cellulosic articles containing small amounts of a surface activeagent comprising the product of reaction of octadecylamine and ethylene oxide possess greatly im- This is true" proved absorbent characteristics. both in the case of otherwise untreated felted cellulosic articles and in the case of such articles which have been treated with sizing agents or with resins which impart wet strength thereto.

Entirely unexpectedly, I have found that only very small amounts of these preferred surface active agents are required to impartgreatly improved absorbency to the cellulos-ic articles treated therewith. The minimum amounts of the surface active agents which are required to obtain these improved results are from about 0.01% to about 1-2% based on the dry weight of the cellulose fibers.

An outstanding feature of this invention is the fact that these octadecylamine-ethylene oxide surface active agents may advantageously be added to the cellulose fibers during the wet processing thereof. Due to the fact that the preferred surface active agents are substantive to cellulose, substantially all of the added agent is uniformly adsorbed by the cellulose fibers. Al-

heated to about 90 C. and ethylene oxide gas was passed into-the kettle. After the reaction. had

started,-the materials were cooled so that the temperature was maintained at from C.1 00

C. After 11.5 hours, the temperature of the r factionmixture was maintained at C.1 00 C. for an additional 2 hours to insure complete reaction of the ethylene oxide. Thereafter the product was stripped of solvent and volatile material by heating to C. under a vacuum of 20-30 mm. Hg. The product contained 3.7 mols of combined ethylene oxide for each mol of octadecylamine and was an orange-brown liquid at room temperature. It was dispersible in cold water and soluble in hot water and dilute acids.

This surface active agent may be added to paper stock or other cellulosic fibers according to the method of the present invention at any desired point during the manufacturing operation as, for example, it may be added to the beater, stool; chest, etc., or it may be added to the final product.

Surface active agents prepared in a manner similar to that described above were employed in the production of a number of absorbent paper products of which the following specific examples are illustrative.

Example 1 Groundwood-sulfite toweling stock was disintegrated in aqueous slurry at about 2.5% consistency to a Green freeness of 200. This slush stock was then diluted to 0.6% consistency. A portion of the stock was withdrawn for the purpose of making paper sheets containing neither resin nor rewetting agent. The remainder of the stock was adjusted to contain about 75 p. p. m. of NazSO; and thereafter a sufficient amount of a 12% aqueous suspension of a melamine-formaldehyde resin-hydrochloric acid colloid was added thereto to insure a resin solids content in the product of 1% of the weight of the fiber. The acid resin colloid employed was prepared as described in U. S. Patent No. 2,345,543. A portion of this resin-treated stock was formed into paper sheets. The remainder of the stock was treated by the addition thereto of amounts of ethylene oxide-octadecylamine rewetting agents varying from 0.02% to 0.3% based on the weight of dry fiber, the molar ratio of ethylene oxide to octadecylamine in the rewetting agents varying from 1:1 to 75:1. In all cases, the pH of the final stock was adjusted to 5.0. Paper sheets were thereafter made on a Nash sheet machine, and the sheets were pressed on a Noble- Wood press, and dried at about 110 C. on a drum drier. The absorption of water by the so prepared sheets was evaluated by dropping 0.03 cc. of water at 73 F. on each sheet, using a calibrated hypodermic needle, and noting the time for absorption thereof. The results are tabuoctadecylamine.

sirable results are obtained when about 5% of such an emulsion, based on the weight of the dry cellulosic fibers, and containing about 100 parts of oil and 20 parts of surface active agent is added to the fibrous cellulose. The following example will illustrate a specific embodiment of my preferred method of applying a mineral oilsurface active agent solution to cellulose fibers.

Example 2 A slush stock was prepared as in the above example. To the stock was added 2% of a melamine-formaldehyde acid resin colloid as described in Example 1. The stock was then treated with an oil-in-water emulsion prepared by adding to warm water a mixture of 100 parts of mineral oil and 20 parts of an octadecylamine-ethylene oxide reaction product having a molar ratio of 3.7 mols of ethylene oxide for each mol of The amount of this emulsion added to the stock was such that the paper sheets prepared therefrom contained 5% of the softening agent. The sheets so prepared were much softer than similar absorbent sheets containing only the wet strength resin and were appreciably softer than similarly prepared untreated sheets.

From a consideration of the foregoing description and illustrative examples, it will be seen that the present invention provides a method of great- 1y improving the absorbency of felted cellulosic articles by the addition thereto of relatively small amounts of an ethylene oxide-octadecylamine condensation product. The preferred surface aclated below. t1ve agents are substantive to cellulose and are TEST RESULTS 003 cc. 1190 at 73 Rewettmg F., Water Drop Tensile Strength, Agent, Mol Percent A b s o r p t 1 o n lbs/inches width Sample Ratio of Percent Rewet- (Seconds) N0. EtO to Resin ting olctadee- Agent y amine Aged 1% New mos. Dry Wet Absorbent felted cellulosic products having improved softness may also be prepared according to the method of the present invention. To this end, I may prepare a solution of any of the above described octadecylamine-ethylene oxide surface active agents in mineral oil and apply this solution to the cellulosic fibers. The mineral oil imparts to the felted articles very desirable hand or softness, overcoming any harshness which may have been caused in the article by the addition of a sizing agent or a wet strength resin, while the surface active agent simultaneously increases the absorbency of the product. The preferred method of applying the mineral oilsurface active agent solution to cellulosic fibers is by first emulsifying the solution and thereafter adding the required amount thereof at any point during the wet formation of the felted cellulosic material. I have found that very detherefore capable of being adsorbed on the cellulosic fibers in aqueous media. Thus, these surface active agents may be added to aqueous slurries of fibrous cellulosic material such as paper stock at any desirable point during the manu facture of felted cellulosic articles. For example, they may be added to the beater, stock chest, head box, or at any other point during the manufacturing operation.

This method of incorporating surface active agents in felted cellulosic materials represents a decided economic advantage over methods heretofore available to the art. Particularly, the method of the present invention eliminates the use of additional equipment such as impregnating machinery and/or equipment employed in the so-called tub sizing method. The method of my invention also obviates the consequent additional drying treatment necessary when these known methods are employed to incorporate addition agents in the felted products.

An even more outstanding and unexpected advantage afforded by the method of the present invention is that the wet strength imparted to felted cellulosic products such as paper, by the application to aqueous suspensions of cellulosic paper stock of 1-5% of the dry weight thereof of the resins described in U. S. Patent No. 2,345,- 543 is not appreciably lowered by the addition thereto of these ethylene oxide-octadecylamine condensation products. This fact is illustrated in the table of Example 1. Thus, I have provided a method of producing absorbent felted cellulosic products, containing small amounts of wet strength resins and surface active agents, which have greatly improved absorbency with little or no loss of wet strength. From a consideration of the examples it will also be noted that my absorbent felted cellulosic products also possess improved softness of hand over prior art absorbent articles containing wet strength resins.

A further advantage to be derived from the present invention is due to the fact that my preferred surface active agents possess lyophilic groups as well as hydrophilic groups, which cause the absorbent paper products made according to my novel method to have improved absorbency for hand lotions, cold creams, facial creams, grease paint, and the like containing vegetable and mineral oils and greases.

While the amounts of the surface active agents to be employed in my novel method may be varied within wide limits as above set forth, for most purposes from about 0.01% to about 0.3% based on the weight of the dry cellulosic fibers, will be sufficient to satisfactorily improve the absorbency of the products. Similarly, while the molar ratio of ethylene oxide to octadecylamine may be varied from about 1 to 2.5 mols to about 75 mols of ethylene oxide per mol of octadecylamine, very satisfactory results have been obtained when from about 3 to 4 mols of ethylene oxide are employed for each mol of octadecylamine in the preparation of the surface active agent.

What I claim is:

1. Absorbent paper composed of felted cellulosic fibers having uniformly adsorbed thereon from about 0.01 to about 1.0% by weight of the condensation product of from 2.5 to 75 mols of ethylene oxide with 1 mol of octadecylamine.

2. Paper according to claim 1 in which the condensation product is the condensation prodnot of 3 to 4 mols of ethylene oxide with octadecylamine.

3. Absorbent paper composed of felted cellumelamine-formaldehyde wet-strength producing resin.

5. Soft paper composed of felted cellulosic fibers having uniformly adsorbed thereon about 5% by weight of a mixture of about parts by weight of mineral oil and about 20 parts by weight of the condensation product of about 3.7 mols of ethylene oxide with about 1 mol of octadecylamine.

6. Soft paper composed of felted cellulosic fibers having uniformly adsorbed thereon about 2% by weight of a cured melamine-formaldehyde wet-strength producing resin and about 5% by weight of a mixture of about 100 parts by weight of mineral oil and about 20 parts by weight of the condensation product of about 3.7 mols of ethylene oxide with 1 mol of octadecylamine.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 792,932 Schmaedel June 20, 1905 1,970,578 Schoeller et al Nov. 24, 1931 1,986,291 Schur Jan. 1, 1935 2,005,397 Schur June 18, 1935 2,136,928 Schlach Nov. 15, 1938 2,213,477 Steindorf et al Sept. 3, 1940 2,291,079 Hofferbert July 28, 1942 2,291,080 Hofferbert July 28,1942 2,315,675 Trommsdorff Apr. 6, 1943 2,325,302 Britt July 27, 1943 2,338,602 Schur A Jan. 4, 1944 2,343,090 Smith Feb. 29, 1944 2,343,095 Smith Feb. 29, 1944 2,345,543 Wohnsiedler et a1. Mar. 28, 1944 2,387,683 Richter et al. Oct. 23, 1945 2,407,376 Maxwell Sept. 10, 1946 2,487,899 Sherman Nov. 15, 1949 2,563,897 Wilson et al Aug. 14, 1951 FOREIGN PATENTS Number Country Date 380,851 Great Britain Sept. 12, 1932 OTHER REFERENCES Lenher, Use of Wetting Agents, Textile Colorist, April 1941, pp. 265-267.

Maxwell, Paper Trade J., May 13, page 41. 

1. ABSORBENT PAPER COMPOSED OF FELTED CELLULOSIC FIBERS HAVING UNIFORMLY ADSORBED THEREON FROM ABOUT 0.01% TO ABOUT 1.0% BY WEIGHT OF THE CONDENSATION PRODUCT OF FROM 2.5 TO 75 MOLS OF ETHYLENE OXIDE WITH 1 MOL OF OCTADECYLAMINE. 